Conventionally, such landing gear comprises a landing gear leg mounted on a structure of the aircraft to pivot about an axis that is essentially perpendicular to the longitudinal midplane of said aircraft, the leg being provided with at least one wheel stub axle and also with an associated driving actuator which is generally extended for the purpose of raising said leg, the hinge point of said actuator being disposed above the pivot axis of the leg.
Numerous landing gears of that type are known in which the leg is resilient, being constituted by a shock absorbing strut hinged to the structure of the aircraft and by a sliding rod fitted with at least one wheel stub axle (the driving actuator then acting directly on the shock absorber strut to bring the leg into a substantially vertical position for landing, or into a substantially horizontal, raised position). The wheel stub axle is generally disposed at the bottom of the sliding rod, or sometimes it is mounted at the end of a rocker hinged to a fork on the shock absorber strut and likewise connected in hinged manner to the sliding rod.
When it is desired to have landing gear capable of coping with a landing under emergency conditions, commonly called a "crash" landing, it is necessary to be able to use a long stroke and also to provide a device for peak-limiting forces, the device being capable of coming into operation quickly in order to cope with the vertical impact speed which is much greater than under normal landing conditions.
Landing gears already exist that are fitted with means for peak-limiting the forces that occur in the event of excessive overpressure, however those landing gears require the undercarriage to be very tall.
With helicopters, and also with certain airplanes, the raisable landing gear is located beneath the cockpit, such that the vertical extent of the landing gear is generally voluntarily kept small so as to reduce the maximum height of the helicopter, both for the purpose of ensuring good stability for the helicopter with its center of gravity being as low as possible, and for making it possible to store the helicopter in warehouses or on the decks of ships where a maximum height is set by doorways.
With the known landing gears as mentioned above, the upper limit is thus given by a wall that corresponds to the floor of the cockpit.
Consequently, the maximum stroke of the resilient leg is limited, e.g. to a value of about 400 mm.